AMPFLP-Typing of the D21S11 Microsatellite Polymorphism: Allele Frequencies and Sequencing Data in the Austrian Population

Human DNA microsatellite polymorphisms (Variable Number of Tandem Repeats, VNTR) with short repeat sizes (2–5bp) have become very useful markers in forensic haemogenetics in the last few years. For a number of reasons, typing for these markers is more and more preferred to conventional techniques in forensic casework: The large number, high polymorphism and thus the high information content of microsatellite markers The use of just one technique (PCR-Amplification Fragment Length Polymorphism, AMPFLP) for all markers The possibility to successfully employ these markers even for very low amounts of highly degraded stains However, it must be stated that there are still some problems and restrictions with these systems. Typing by AMPFLP on polyacrylamide gels is not always very clear-cut, especially with certain markers (e.g. APOB, SE33) because of interalleles (variants with incomplete repeats or sequence variants with distinct electrophoretic mobility) and/or the limited resolution capability of electrophoresis. The allele frequency distribution in different populations has shown significant differences for certain systems, whereas other loci showed a more uniform distribution, at least in the populations studied so far. Since the amount of data is limited, especially for the microsatellites with short core repeat length (Short Tandem Repeats, STR) population studies are still required. Furthermore, detailed sequencing studies should also be performed for all markers in forensic use since only with this technique the polymorphism can be determined to the ultimate level. For routine use the AMPFLP technique will still stay the standard, but it is required that a marker consisting of alleles with known sequence is used with this technique [DNA comission of the ISFH, 1994].